1. Emmanuel Ohene Afoakwa* & Philip Roger Aidoo RESULTS AND DISCUSSION
EFFECT OF FERMENTATON ON THE PHYSICO-CHEMICAL AND FUNCTIONAL PROPERTIES OF NIXTAMALIZED MAIZE
Emmanuel Ohene Afoakwa* & Philip Roger Aidoo
Department of Nutrition & Food Science, University of Ghana, Legon-Accra. *
ABSTRACT
UNIVERSITY OF GHANA
This study was carried out to determine the extent to which water and coconut water could be used as fermentation media during souring or acidification of nixtamalized maize and their effect on the chemical and functional properties of the nixtamalized maize. A 2 x 3 x 3 factorial experiment with fermentation medium (water, coconut water), fermentation time (0, 24, 48 hours) and blends composition (0:100, 50:50, 100:0 steeped:nixtamalized maize) was performed. The blends were fermented for the specific times and analysed for pH, titratable acidity, water absorption, colour and texture. Traditional maize dough facilitated the fermentation process by acting as a starter culture to produce lower pH and higher acidity in the steeped:nixtamalized maize blends. The fermentation time and blend composition significantly (p<0.05) influenced the pH, titratable acidity, water absorption capacity, colour and texture of the samples. The pH of all the blends decreased from 6.24 to 4.22 and 4.83 to 4.20 with corresponding increases in titratable acidity from to g Lactic/100g sample and to respectively for samples fermented in coconut water and water, as fermentation time was increased. There was however no significant (p<0.05) difference in the effect of fermentation medium on the colour and texture of the products, indicating adequate souring for improved product during processing.
INTRODUCTION
RESULTS AND DISCUSSION
Maize (Zea mays) or corn is the most important cereal grain in tropical Africa.
It is vital for the survival and food security of a large segment of Africans.
Traditionally, fermentation of maize is carried out spontaneously and the derived meal forms the basis of most of the maize based products consumed in Africa.
Fermentation has also been identified to significantly improve the nutritional value (protein quality) of maize-based foods and as well reduce their anti-nutritional factors resulting in desirable changes in colour, flavour and texture (Bressani et. al., 1990; Afoakwa et al., 2004).
Nixtamalization is applied to maize to increase niacin bioavailability, improve protein quality and the reduce aflatoxins concentration (Serna-Saldivar et al., 1990).
Nixtamalized corn is used in making breakfast gruels like “atalo” and “pinole”, soups like “pozol”. The most significant industrial advancement in the use of nixtamalization is the production of Dry Masa Flour (DMF), a shelf stable nixtamalized product (Serna-Saldivar et al., 1990; Afoakwa et al., 2002).
The rationale for this study was to investigate the effect of fermentation on the physico-chemical, functional and textural properties of nixtamalized maize.
Fig 1. Changes in pH and titratable acidity during fermentation of nixtamalized maize
MATERIALS AND METHODS
Materials
Maize (Zea mays) and coconut were obtained from the Crop Research Institute in Ghana, and stored at cold room temperature (4 °C) during the experimental period.
Lime (Ca (OH)2) food grade, was obtained from BOH chemicals Ltd; Poole, England.
Experimental Design
A 2 x 3 x 3 factorial experimental design was used.
The principal factors investigated were:
i. Fermentation medium: Water and Coconut water.
ii. Fermentation time: 0, 24, 48 hours.
Iii. Conc. Of fermented dough in mixture: 0, 50, 100%
Fig 2. Changes in water absorption capacity (27 & 70 ˚C) during fermentation
Methods
Physico-chemical properties pH
Titratable acidity
Functional properties
Water absorption capacities at 25°C and 70°C.
Colour
TheColorimetric measurements of the dry flour samples were recorded using Minolta CR-310 tristimulus colorimeter (Minolta Camera Co ltd, Osaka, Japan).
Texture
The texture of the slurries were determined using TA-XT2 Texture Analyser, equipped with back extrusions rig with a compression disc of 45 mm diameter.
Statistical analysis
The data were statistically analyzed using Statgraphics (Graphics Software System, STCC, Inc. U.S.A). Comparisons between sample treatments and the indices were done using analysis of variance (ANOVA) with a probability p<0.05.
Fig 3. Changes in colour and texture during fermentation of nixtamalized maize
Fermentation of the nixtamalized maize resulted in decreased pH, with concomitant increases in water absorption capacity, colour intensity (L - value), texture and titratable acidity.
Nixtamalization increased the pH, water absorption capacity and produced a yellowish colour in the nixtamalized maize.
Fermenting the nixtamalized maize caused increases in acidity in both media and the results from coconut water was not different from those for water. Coconut water can therefore be exploited for use as effective fermentation medium in places where water availability is limited.
The low pH and high lactic acid formation in the fermented nixtamalized maize systems suggests that fermented nixtamalized maize possesses the sour aromatic flavour and antimicrobial properties exhibited in traditional fermented maize dough.
ACKNOWLEDGEMENT
CONCLUSION
Fermentation can be applied to nixtamalized maize using water and coconut water to effectively produce adequate souring / acids with improved functional properties to serve as alternative means of industrial processing maize for a wide variety of products.
Many thanks to the International Nutrition Foundation, USA for financial support.
Presented at the 13th World Food Congress, September , 2006, Nantes, France